giantess step-sister shrinks step-brother and surprise you

Your step-sister gives you your favorite drink, but what you don't know is that she added something to your drink. So that takes effect very quickly and you feel like you are shrinking little by little, and she acts like she doesn't know anything, and she just makes fun of you because you fell into her trap, now she was going to have fun with you because you are very small and you can't defend yourself